lkml.org 
[lkml]   [2009]   [Jun]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v3] printk: add halt_delay parameter for printk delay in halt phase

* Dave Young <hidave.darkstar@gmail.com> wrote:

> Add a halt_delay module parameter in printk.c used to read the
> printk messages in halt/poweroff/restart phase, delay each printk
> messages by halt_delay milliseconds. It is useful for debugging if
> there's no other way to dump kernel messages that time.
>
> The halt_delay max value is 65535, default value is 0, change it
> by:
>
> echo xxx > /sys/module/printk/parameters/halt_delay
>
> Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
> ---
> Documentation/kernel-parameters.txt | 5 +++++
> kernel/printk.c | 17 +++++++++++++++++
> 2 files changed, 22 insertions(+)
>
> --- linux-2.6.orig/kernel/printk.c 2009-06-08 13:55:35.000000000 +0800
> +++ linux-2.6/kernel/printk.c 2009-06-08 13:56:23.000000000 +0800
> @@ -250,6 +250,22 @@ static inline void boot_delay_msec(void)
> }
> #endif
>
> +/* msecs delay after each halt/poweroff/restart phase printk,
> + unsigned short is enough for delay in milliseconds */
> +static unsigned short halt_delay;
> +
> +static inline void halt_delay_msec(void)
> +{
> + if (unlikely(halt_delay == 0 || !(system_state == SYSTEM_HALT
> + || system_state == SYSTEM_POWER_OFF
> + || system_state == SYSTEM_RESTART)))
> + return;

This is a tiny bit ugly (and goes into the vprintf path) but i can
see no other way either - a system_state > SYSTEM_RUNNING check
would needlessly include the suspend-to-disk state (which we dont
want to include here).

In theory we could turn system_state into a bitmask and have a
print_delay_mask check instead of these flags ... but that is a far
wider change and i'm not sure it's a net step forwards.

I've applied your patch to tip:core/printk with small edits to the
changelog - Linus & Andrew is Cc:ed, should they have any
objections.

Ingo


\
 
 \ /
  Last update: 2009-06-08 10:17    [W:0.099 / U:0.048 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site